One of the highest-profile members of the British National party has been banned from sitting on his local council for a month and censured by the Greater London authority after giving false details about murders on a video blog.

Richard Barnbrook, who holds a seat on Barking and Dagenham council and is the BNP's only London assembly member, brought his position, the GLA and his council into disrepute, a disciplinary hearing found yesterday.

Barnbrook was suspended from the council for a month and must apologise, but the GLA stopped short of a ban, instead warning him about his behaviour and demanding a written apology.

The complaint against Barnbrook was first lodged last September after he claimed in an interview, posted on YouTube and his own website, that a girl had been murdered in the borough within the past three weeks.

"We don't know who's done it. Her girlfriend was attacked inside an educational institute," Barnbrook said in the prerecorded interview, in which he sought to highlight failings in tackling knife crime.

He also said that, two weeks previously, "there was another attack by knives on the streets of Barking and Dagenham where two people were murdered".

The Metropolitan police confirmed that there had been no murders or incidents resulting in critical injuries requiring intensive care in the period cited by Barnbrook, and said murders in the area were actually decreasing.

Valerie Rush, a Barking and Dagenham Labour cabinet member, accused Barnbrook of "openly and outrageously" lying to "whip up fears in the London community".

"I firmly believe that he outrageously and knowingly lied on the video," she told the hearing.

"I believe that he did that with the firm intention of whipping up fear on the streets of Barking and Dagenham and across London.

"We went, as a capital city, through about a year to 18 months of horrendous stories of young people losing their lives on the streets of London through knives, and I think councillor Barnbrook was trying, through his video, to whip up even more fear in the community."

After the hearing, Barnbrook described the process as a waste of taxpayers' money.

He said he would appeal against the findings, adding: "In that room there are quite a few academic, brilliant brains, I'm sure, but I think it was a total waste of taxpayers' money and resources to have this kangaroo court set up against me."

He said he had made "unintentional inaccuracies" because he was dyslexic and was confused by loud background noise as the film was made.

The first murder took place in another area, he said, and the other two "killings" were attempted murders.

Barnbrook apologised for using incorrect information and said he would continue to highlight the issue of knife crime.